WO2011124858A1

WO2011124858A1 - Estimation of the temperature outside a vehicle from temperature measurements under the bonnet of a vehicle

Info

Publication number: WO2011124858A1
Application number: PCT/FR2011/050791
Authority: WO
Inventors: François FOUSSARD; Stéphane Guegan; Nicolas Romani; Philippe Saint Loup
Original assignee: Renault S.A.S.
Priority date: 2010-04-08
Filing date: 2011-04-07
Publication date: 2011-10-13
Also published as: BR112012025438A2; EP2555956B1; CN102939232B; CN102939232A; RU2561486C2; FR2958610B1; US20130066583A1; EP2555956A1; RU2012147488A; FR2958610A1

Abstract

The invention relates to a method for determining an estimated value of the air temperature outside a vehicle (1) driven by an internal combustion engine (5), according to which an initial estimated value is attributed to the estimated temperature, the temperature of the intake air of the engine (5) is then measured, and the speed of the vehicle (1) is assessed. This is followed by a mathematical filtering of the measured temperature of the intake air of the engine (5), said filtering operation imposing a maximum gradient on the estimated temperature, that has at least two separate positive values over time, either one of said maximum positive gradient values being selected according to the momentary speed of the vehicle (1).

Description

Estimation of the temperature outside a vehicle from temperature measurements under the engine bonnet of the vehicle.

The invention lies in the field of temperature monitoring of the mechanical components of a vehicle powered by an internal combustion engine. In order to estimate the temperature of these organs, the thermal energy dissipated by friction in these organs is generally calculated, and the thermal energy evacuated by contact with the air surrounding the organ, ie the air under the bonnet or the air outside the vehicle. In the case of four-wheel drive vehicle, it is thus necessary to calculate the temperature of a coupler, transmitting the available engine torque on a wheel train to the other wheel set of the vehicle. In this case in particular, the temperature outside the vehicle is an essential data for reliably calculating the heating of the coupler.

For reasons of reducing the manufacturing cost and the cost of maintaining the vehicle, the number of temperature sensors installed on the vehicle is strictly limited. It is thus desired to have monitoring methods that make it possible to dispense with a sensor on the member (for example on the coupler) to be monitored, but which also makes it possible to dispense with a temperature sensor outside the vehicle, all the more so since such an outdoor temperature sensor is necessarily subject to external aggression which limit its accuracy.

The patent application EP 1 308 336 describes a method of managing a coupler as a function of its heating, as well as a method for calculating the temperature rise as a function, among other parameters, of the temperature outside the vehicle.

US patent application 2004/0184509 proposes to calculate the temperature of the air outside the vehicle from the air temperature measured in an air intake pipe to the engine. When starting, the system initializes the temperature, either at the last stored temperature or at the temperature measured at the time of admission. start time, choosing the lower of these two values. The system then monitors the probability that a steady state will be established, including monitoring the vehicle running time, the instantaneous vehicle speed, and the amount of air entering the engine. If the instantaneous speed is below a certain threshold, or the intake airflow is below another threshold, an incremental value of superheat is arbitrarily added to the incoming air temperature value relative to the temperature value. outside air. The intake air temperature in the engine is used as a valid estimate of the outside air temperature when the calculated superheat value is sufficiently low. This method has the disadvantage of underestimating the outside air temperature, therefore that of the organs cooled by this outside air. In addition, it requires the existence of a flow sensor on the air intake circuit in the engine.

The patent application US 2005/0071074 proposes to estimate the outside air temperature from a temperature measured at the inlet of a turbocharger, by correcting this input temperature of the turbocharger according to the operating parameters, therefore, the potential for heating the engine compartment, and also correcting it as a function of the activation or inactivation of a cooling fan of the engine compartment. The document does not specify how the initial outdoor temperature value is determined when the temperature estimate begins. The proposed method requires the use of algorithms or temperature correction charts, depending on the engine speed and the activity of the fan, and requires calculation means fast enough to take into account these algorithms or charts. . In addition, these algorithms and charts will be specific to a given vehicle model.

The aim of the invention is to propose a method of estimating the temperature of air outside a vehicle, making it possible to have an estimated temperature value as soon as the vehicle is started. The method must be sufficiently precise during the running of the vehicle, and sufficiently secure at the time of starting to avoid a risk of overheating of a body following a warm start of the vehicle.

In a method for determining an estimated value of the outside air temperature of a vehicle driven by an internal combustion engine, an estimated initial value is attributed to the estimated temperature, and then the air temperature admitted into the engine is measured. and the speed of the vehicle is evaluated. A mathematical filtering of the measured temperature of air admitted into the engine is carried out, the filtering imposing on the temperature a maximum gradient taking over time at least two different positive values, one or other of these values of maximum positive gradient being selected according to the instantaneous speed of the vehicle.

According to a preferred embodiment, an initial intake air temperature is measured in the engine and an initial coolant temperature has remained in the engine cooling circuit, and an initial estimated value is deduced from these two values. temperature.

Advantageously, a first maximum temperature threshold is imposed at the estimated air temperature and at its initial value.

The value of the first maximum temperature threshold can be imposed on the initial estimated temperature value, in particular if the difference between the initial air temperature admitted into the engine and the initial coolant temperature is greater than a second. gap threshold.

It is also possible to impose the first maximum temperature threshold at the initial estimated value, if the initial air entering temperature is greater than a third threshold, or if the initial coolant temperature, is greater than a fourth threshold.

According to a preferred embodiment, the initial intake air temperature in the engine, or the initial coolant temperature, is taken as the initial estimated value, when the difference between these two temperatures is lower than the second threshold of the engine. gap. Advantageously, the estimated temperature is equal to the air temperature admitted into the engine over the periods of time when the air temperature admitted into the engine is decreasing,

At least two different maximum positive gradients can be imposed at the estimated temperature as it increases, and at least one minimal negative gradient when the estimated temperature decreases, the negative gradient being in absolute value greater than at least ten times each of the two gradients positive.

According to a preferred embodiment, the filtering imposes a first maximum positive gradient of between 0.001 ° C / s and 0.01 ° C / s, and a second maximum positive gradient which is a multip le of the first positive gradient by a number included between 2 to 5.

The method can be applied to a torque transfer coupler between two sets of wheels of a vehicle, using a method for estimating the temperature of air outside the vehicle as described above.

According to another aspect, a system for determining an estimated value of the outside air temperature of a vehicle driven by an internal combustion engine comprises an air temperature sensor admitted to the engine, a liquid temperature sensor. engine cooling system, a device for evaluating the instantaneous speed of the vehicle, an initialization module able to determine an initial temperature from an initial temperature of air admitted to the engine and an initial temperature of the liquid cooling. The system also comprises an estimation module capable of mathematically filtering the temperature of the air admitted into the engine, so as to impose on the filtered value a maximum gradient taking over time at least two different positive values, one either of these maximum positive gradient values being selected according to the instantaneous speed of the vehicle.

Other objects, advantages and features of the invention will become apparent upon examination of the detailed description of some embodiments of the invention. embodiments given by way of nonlimiting example, and illustrated by the accompanying drawings, in which:

Figure 1 illustrates a four-wheel drive vehicle equipped with an external temperature estimation system according to the invention;

FIG. 2 illustrates an example of curves of variation of coolant temperature, of the air temperature admitted into the engine, and of the estimated temperature of the outside air, recorded or calculated on the vehicle of FIG. 1; FIG. 3 illustrates the operation of an initialization module belonging to a system for estimating the temperature according to the invention;

FIG. 4 illustrates the operation of a calculation module running the temperature outside the vehicle belonging to a system for estimating the temperature according to the invention.

As illustrated in FIG. 1, a vehicle 1 comprises a front wheel train 2 and a rear wheel train 3, the front axle 2 and the rear axle 3 being connected by a coupler 4 able to fully or partially rotate together. the front axle 2, and the rear axle axle 3. Each of the front wheels 2 is provided with a rotational speed sensor 12 and each of the wheels of the rear axle 3 is provided with a speed sensor. speed of rotation 13. The values recorded by the sensors 12 and 13 make it possible in particular to calculate the difference in speed of rotation between the front axle axis 2 and the rear axle axis 3, as well as the instantaneous speed of the vehicle 1 . Such sensors are generally present on the four wheels of a four-wheel drive vehicle, or more generally on the four wheels of vehicles equipped with an ABS traction control system, or a system for correcting the trajectory of the vehicle. ESP type. The axis of the nose gear 2 is connected by a transmission system (not shown) to an internal combustion engine 5, including an air inlet 6, bringing fresh air through a air filter 9 to cylinders 7 of the engine. The engine 5 is equipped with a coolant circuit 10. A temperature sensor 8 is disposed at the level of the air intake circuit 6, between the air filter 9 and the inlet of the cylinders 7. A sensor temperature 11 is disposed in the vicinity of the engine 5 in contact with the liquid of the cooling circuit 10. The wheel speed sensors 12 and 13, and the temperature sensors 8 and 11, are connected by connections 16, 17, respectively. 14, 15 to an electronic control unit 18. The electronic control unit 18 comprises in particular a module 21 for estimating the instantaneous speed of the vehicle, the module 21 being connected to the connections 16 and 17 of the wheel speed sensors. The electronic control unit 18 also comprises an initialization module 19 connected by the connections 14 and 15 to the two temperature sensors 8 and 11, and a current current temperature estimation module 20, the module 20 being connected. by a connection 16 to the air temperature sensor 8 admitted to the engine. The current temperature estimation module 20 is further connected to the other two initialization and 19 vehicle speed estimation modules 19. When, after a stopping of the vehicle, the engine 5 is started, the initialization module 19 is activated. It then records an initial temperature value of air admitted into the engine, which is transmitted to it by the sensor 8, and an initial temperature of coolant, which is transmitted to it by the sensor 11. From these two values, the initialization module 19 calculates an initial air temperature value outside the vehicle that it transmits to the current temperature estimation module 20.

Once the vehicle is in motion, the estimation module 20 periodically receives an estimated instantaneous speed value of the vehicle of the module 21, and a measured value of the air temperature admitted into the engine from the sensor 8. estimation module 20 performs a mathematical filtering of the value arriving at it from the sensor 8, the filtering modalities being adapted according to the current value of the instantaneous speed of the vehicle, and dependent on the initial temperature value transmitted to it by the initialization module 19. The value thus filtered can be considered as an estimate of the outside air temperature of the vehicle, and can be used, for example, to display a display of information for the driver, or for estimating temperatures of different dissipative mechanical members, for example the one or more temperatures internal to a torque transfer coupler 4 between a front axle 2 and a rear axle 3 of the vehicle.

FIG. 2 shows, over a time interval AG including rolling phases of the vehicle 1 of FIG. 1, an example of an actual outside temperature curve 27, and measured or estimated temperature curves 25, 26 and 28. AG time interval includes the following driving sequences:

In A, the vehicle 1 starts after a long stop and travels to the instant B at a speed below 15 km / hour. On the BC interval, the speed of the vehicle constantly keeps values higher than 15 km / hour. Over the time interval CD, the vehicle slows down and its speed V becomes less than 15 km / hour. At time D, the vehicle stops, the engine is off and the vehicle remains stationary until time E. At the moment E the vehicle restarts and circulates at a speed lower than 15 km / hour until the moment F. Between moment F and instant G, the vehicle resumes a cruising speed higher than 15 km / hour.

The curve 27, indicating the temperature outside the vehicle, is given purely theoretical, since it is not directly accessible. However, it is represented because it influences the evolutions of the other measured temperatures. The curves 25 and 26 respectively represent the coolant temperature delivered by the sensor 1 1 of FIG. 1, and the temperature of air admitted into the engine, delivered by the sensor 8 of FIG. At start A of the vehicle, the curves 25, 26 and 27 are close to each other because the coolant, the pipes in which circulates the air admitted into the engine, and the entire engine compartment, have substantially reached a thermal equilibrium with the air outside the vehicle.

After starting the vehicle at time A, the temperature indicated by the coolant curve 25 increases to a temperature which may be close to 90 °, and remains close to these values until it stops at a temperature of 90 °. moment D of the vehicle. The period of time DE during which the vehicle is stopped does not allow complete cooling of this coolant, so that at the time of the restart E of the vehicle, the coolant temperature is still relatively high, for example here above 75 °.

After starting the vehicle at time A, the temperature of the air admitted into the engine, given by the curve 26, increases initially up to about 50 °, since the ducts in which the intake air circulates. heat up at the same time as the entire engine compartment. During the subsequent driving of the vehicle, and with the speed increase of the vehicle over the time interval BC, the flow of air flowing under the engine hood makes it possible to limit the heating of the parts under the bonnet, which reduces the difference temperature between the temperature of the curve 26 indicating the temperature of air admitted into the engine, and the temperature 27 of air outside the vehicle. The difference between the outside air temperature of the vehicle and the intake air temperature, however, continues to oscillate, for example due to changes in temperature under the bonnet caused by changes in the engine speed.

During the second start of the vehicle at time E, the engine compartment is still at a temperature substantially higher than the outside air temperature of the vehicle, so that the air temperature 26 admitted into the engine is in a first time relatively high (above 50 ° C), before decreasing to values close to 30 °, once sufficient air circulation is established under the bonnet when the vehicle has reached a higher cruising speed at 15km / h. Curve 28 represents the estimated air temperature outside the vehicle, obtained by mathematical filtering of the curve 26 by means of the estimation module 20. At the time of starting A of the vehicle, an initial temperature value 29 is delivered to the module. estimation 20 by the initialization module 19 of FIG. The initial value 29 is here equal to the temperature measured for the air admitted to the engine at the time of starting, because the initialization mode, by comparing the temperatures of coolant and air admitted to the engine, concludes that the vehicle had time to cool down to room temperature.

After starting the vehicle, as long as the temperature of the recorded curve 26 remains higher than the last temperature calculated for the curve 28, the estimation module 20 increments, at each instant of calculation, the estimated temperature 28, so that that this curve 26 has a maximum slope a. Once curve 28 has joined curve 26, for example at points 31, 32 or 33, curve 28 then follows curve 26 as long as the gradient of curve 26 remains below the maximum gradient imposed a. The two curves therefore remain confused as the curve 26 decreases, or the curve 26 grows less quickly than the imposed maximum gradient.

The maximum gradient imposed on the curve 28 varies as a function of the instantaneous speed V of the vehicle. In the example illustrated in FIG. 2, this gradient takes two distinct values, the first gradient value corresponding to velocities V less than 15 km / hour, that is to say at the time intervals AB, CD and EF; and the second gradient value corresponding to instantaneous velocities greater than 15 km / hr, i.e. in Figure 2 at time intervals BC and FG.

When the vehicle restarts at time E, the initialization module 19 delivers a new initial value 30 of outside air temperature to the vehicle. The current estimation module 20 uses the initial value 30 to start again filtering the values of the curve 26 according to the process explained above. In the case illustrated in FIG. 2, during this second start the coolant temperature and the air temperature admitted into the engine are relatively high. The initialization module 19 then assigns an arbitrary maximum value to the initial temperature 30.

FIG. 3 schematically illustrates a possible operating mode of the initialization module 19 of the electronic control unit 1 8 of FIG. 1. FIG. 3 shows some elements common to FIG. 1, the same elements then bearing the same references. The initialization module 19 has, in a read-only memory 39, calculation parameters ΔΤ, T _LM and T _MAX . Once the combustion has started in the engine cylinders, a z status counter is initialized to zero in step 40, and the initialization module 19 receives through the connections 14 and 15 a measured value T _a i _r (z) representing the temperature of air admitted into the engine, and a measured value Tn _q (z) representing the temperature of the coolant in the vicinity of the engine. In step 41, these measured values are assigned to initial values T _r _a i _n i _i and Tn _q _{_ί} η1. In steps 42 and 43, tests are performed on the values T _a _{r jn} i and Tn _{q jn} i to determine in steps 44 and 45 which of the two values of T _a i _r i _n i, measured by the sensor 8, or T _max stored in the memory 39, will be assigned to the variable T _f ii _be (0) which will be used subsequently by the mo dule 20 as an initial value of temperature outside the vehicle. According to test 42 and 43, the initial value I _r i _n d i of temperature 'intake air is selected as the initial value T _f ii _be (o) if the two following conditions are fulfilled simultaneously:

-the temperature difference between the initial temperature of intake air _T i _{r jn} i and the initial temperature Tn _{q jn} i coolant is lower in value abso ΔΤ read a value stored in the ROM 39;

the value Tn _{q jn} i of coolant is lower than a maximum value stored in the read-only memory 39.

If either of these conditions is not realized, an arbitrary value T _max also stored in read-only memory 39, is assigned to the initial value Tfii _tre (o) of the estimated outside temperature. FIG. 4 schematically illustrates a possible operating mode of the module 20 for estimating the current temperature outside the vehicle. Figure 4 shows elements common to Figure 1, the same elements being designated by the same references. The estimation module 20 has, in a ROM 49, _m Vn calculation parameters, T _max, a and A. When the module initialization 19 of Figure 1 has determined an initial value T _f ii _be (0 ), it forwards the estimation module 20 in step 50. This initial value T _f ii _be (0) is assigned to an intermediate variable calculating T _c, at the same time that an indicator state is z forced to zero.

In step 5 1, the status indicator z is incremented by one unit, and the estimation module 20 receives, via the connection 14 connecting it to the sensor 8 of FIG. 1, a current value T _a i _r (z) representing the air temperature admitted into the engine. The module 20 also receives from the speed estimation module 21 a value V (z) giving the instantaneous speed of the vehicle. The values T _a i _r (z), T _c and V (z) acquired in step 52 are then subjected to the tests at steps 53 and 54, from which or to a step 57 directly attributed to the value filtered current T _f _be ii (z) the value T _a i _r (z) of air admitted into the engine, increased if necessary by a value T _max maximum acceptable temperature; or it is decided to perform, in a step 58, a filtering on the slope of the estimated outside temperature, the maximum slope values a or A being previously selected in steps 55 and 56. Step 57 is triggered if the test 53, the air temperature measured at the inlet T _a i _r (z) is less than or equal to the temperature T _c estimated at the previous step.

In the opposite case, the test 54 is triggered, to select a first value "a" of gradient, if the instantaneous speed V (z) of the vehicle is less than or equal to a speed Vn _m , and to select a gradient value " A "otherwise.

The values a, A, Vn _m , are parameters stored in the read-only memory 49. In step 58, the gradient α or the gradient A is used to increment the estimated value T _c for the previous status indicator z , to obtain a value T _f i _lter (z), corresponding to the current status indicator z.

The filtered value, or directly replicated to the air temperature measured at the inlet of the motor is then assigned to a current value of estimated external temperature T _f i _lter (z). In any case, the estimated temperature T _f i _lter (z) is bounded by the value T _max maximum acceptable temperature, which is a constant stored in the ROM 49. The estimated value of temperature T _f i _ltre (z) is then assigned to the intermediate calculation variable T _c . The process then resumes in step 5 1, by incrementing the status indicator z. The value T _f i _lter (z) representing the estimated outside temperature can then be transmitted to other calculation modules, for example estimating dissipative organ temperatures. For the sake of safety, it is possible to systematically increase the value T _f i _ltre (z) by adding a positive increment δ constant, representing for example a measurement uncertainty related to the sensor 8. It will thus be avoided to underestimate the temperature mechanical parts which one wishes to avoid overheating. The increment δ can be added before or after thresholding the outside temperature value T _f i _lter (z) by the maximum threshold value T _max . In summary, it can be said that the estimated temperature value is, on the one hand, increased in value by the measured temperature of air admitted into the engine, this increase taking place following the test 53 in step 57; and on the other hand, that the estimated temperature value is increased in terms of slope or derivative, by at least two different positive gradient values a and A. This slope increase occurs at step 58, after having selected the appropriate gradient value in steps 55 or 56. In the example illustrated in FIG. 4, two different positive gradient values a and A are imposed according to whether the instantaneous speed V of the vehicle is greater or less than a threshold speed V n _m .

The maximum allowed gradient value "A" for speeds higher than Vn _m , is itself higher than the gradient value "a" allowed for lower speeds, because the higher the As the vehicle moves quickly, it is considered that it is possible for a positive variation in temperature to reflect an effective variation of the outside temperature, and not just for the temporary heating of the elements present under the bonnet. It is possible to envisage alternative embodiments in which several limit speeds, each corresponding to a transition from a maximum gradient to another maximum gradient, are defined. It is also possible to envisage variants in which a minimum negative gradient is imposed at the estimated temperature T f (z) so as not to pass on to this estimated temperature certain noises of acquisition of the values delivered by the temperature sensor. . By way of example, for the parameters shown in FIG. 3 of FIG. 3, the following values can be taken:

With regard to the maximum temperature difference ΔΤ between the initial engine liquid temperature and the initial intake air temperature in the engine, values between 5 and 20 °, or more preferably between 10 and 15 °, may be used.

With regard to the T _LM value of maximum coolant temperature above which it is considered that the air temperature admitted into the engine can no longer be accepted as the ambient air temperature, values between 20 and 50 ° according to the climate of the country where the vehicle is traveling, for example 30 ° for a country of Western Europe.

Concerning the _maximum temperature T _max value acceptable for the estimated outside temperature of the vehicle, it will be possible to take values between 40 ° and 60 ° for a vehicle traveling in a temperate country, for example a value of 50 °.

With regard to the increment value δ to systematically add to the estimated outside temperature, a value will be taken that depends on the accuracy of the temperature sensor 8. The value of δ may be for example of the order of 10 ° C.

Concerning the parameters stored in memory 49 for the current estimation module 20 of FIG. 4, it will be possible to take the same estimated maximum temperature value T _max as for the initialization module 19 of Figure 3; The following threshold speed and maximum gradient values may also be chosen: the threshold speed must be a speed of between 10 and 30 km / h, for example 15 km / h; the first maximum positive gradient value "a" applied when the speed is lower than the speed Vii _m may for example be between 0.001 ° C / second and 0.01 ° C / second, for example equal to 0.006 ° C / second ; the gradient A corresponding to the higher speeds may for example be between 0.005 ° C / second and 0.05 ° C / second and be for example equal to 0.017 ° C / second.

In the case, not mentioned in FIG. 4, where a negative minimum gradient imposed on the estimated external speed is also chosen, this minimum negative gradient may be chosen as an absolute value equal to a multiple of between 10 and 100 the maximum gradient A. For example, in the case where the maximum gradient A is equal to 1 ° C / minute, the minimum gradient can be taken equal to -1 ° C / second.

The invention is not limited to the embodiments described, and can be declined in many variants by adding additional filtering filterings already described. In the case of a vehicle other than a four - wheel drive vehicle or a vehicle equipped with ABS or ESP, the instantaneous speed of the vehicle can be simply deduced from the speed of rotation of an account. single tower placed at one of the wheels or at one of the axles. It is possible, whenever a measurement where an evaluation is made and transmitted, to transmit simultaneously with the measured or estimated value, a boo lean validity indicator allowing to translate whether the estimated or measured value presents a level of credibility enough or not. The estimated or measured value is then processed in the next step, differently depending on its level of credibility. The different threshold values and gradient values, may take values other than those proposed or be adapted for the same vehicle depending on the season. The evaluation system according to the invention uses a minimum number of input data, these input data being available by default on most existing vehicles. The reduced number of sensors involved, and the simplicity of the algorithm, ensure great robustness to the system. The choice of an initial temperature which is deliberately overestimated as soon as it is prejudged that the engine compartment has not had time to cool down to the ambient temperature, also leads to overestimating the temperature of the dissipative mechanical members, the less during the phase immediately following engine start. This choice leads to imposing on these mechanical devices, operating modes with limited energy dissipation, so as to prevent their overheating. The system for estimating the temperature outside the vehicle according to the invention is therefore robust, economical, and safety factor.

Claims

1. A method of determining an estimated value (T _f i _ltre (z)) of air temperature outside a vehicle (1) driven by an internal combustion engine (5), in which an estimated initial value (T _f iit _r e (O)) at the estimated temperature, then the intake air temperature (T _a i _r (z)) in the engine (5) is measured and the speed (V (z)) of the vehicle is evaluated , characterized in that a mathematical filtering of the measured temperature (T _a i _r (z)) of air admitted into the engine (5) is carried out, the filtering imposing on the estimated temperature (T _f n _tr ( z)) a maximum gradient taking over time at least two different positive values (a, A), one or the other of these maximum positive gradient values being selected according to the instantaneous speed (V (z) ) of the vehicle.

2. Air temperature determining method outside according to claim 1, wherein an initial temperature is measured _(T i _r i _jn) of air taken in the engine (5) and an initial temperature (Tn _q _i _n i) coolant having remained in the cooling circuit (10) of the engine (5), and deduced from these two values an initial estimated value of temperature (T _f i _ltre (0)).

3. Method for determining the outside air temperature according to one of the preceding claims, in which a first maximum temperature threshold (T _max ) is imposed on the estimated air temperature (T _f i _lter (z)) and at its initial value (T _f i _lter (0)).

4. A method for determining the outside air temperature according to one of claims 2 to 3, wherein the value of the first threshold (T _max ) of maximum temperature is imposed on the initial estimated value of temperature (T _f i _ltre ( 0)), in particular if the difference between the initial intake air temperature (T _a i _n _r _i i) in the motor (5) and the initial temperature coolant (Tn _{q jn} i) is greater than at a second difference threshold (ΔΤ).

5. Method for determining the outside air temperature according to claim 4, in which the value of the first maximum temperature threshold (T _max) to the initial estimated value (T _f ii _be (O)), Silate mp e r atur ein it ialed the area ntr ant (T _a i _r _i _nl) is greater than a third threshold ( T _LM ), OR if the initial coolant temperature, is greater than a fourth threshold (T _LM ).

6. A method of determining outside air temperature according to claims 4 or 5, wherein one takes as the initial estimated value (T _f ii _be (0)), the initial temperature of intake air (T _a i _r i _jn ) in the engine (5), or the initial temperature (Tn _{q jn} i) of coolant, when the difference between these two temperatures is lower than the second difference threshold (ΔΤ).

7. A method for determining the outside air temperature according to one of the preceding claims, wherein the estimated temperature (T _f _iitre (z)) is equal to the air intake temperature (T _a i _r (z) )) in the engine (5) over the periods of time when the intake air temperature in the engine (5) is decreasing,

8. air temperature determination method outside according to Claims 1 to 6, in which imposes at least two different maximum positive gradients (a, A) to the estimated temperature _(f _be ii (z)) when the latter grows, and at least one minimal negative gradient when the estimated temperature decreases, the negative gradient being in absolute value greater than at least ten times each of the two positive gradients.

9. A method for determining the outside air temperature according to one of the preceding claims, wherein the filtering imposes a first maximum positive gradient (a) between 0.001 ° C / s and 0.01 ° C / s, and a second gradient. positive maximum (A) which is a multiple of the first positive gradient by a number between 2 to 5.

10. Method for estimating at least one internal temperature of a coupler (4) for transfer of torque between two wheels (2, 3) of wheels of a vehicle (1), using a method for estimating the temperature outside air to the vehicle according to one of claims 1 to 9.

1 1. System for determining an estimated value of outside air temperature for a vehicle (1) driven by a motor (5) to internal combustion, comprising a sensor (8) of air temperature admitted into the engine, an engine coolant temperature sensor (11) (5), a device (21) for evaluating the instantaneous speed (V) (z)) of the vehicle, an initialization module (19) able to determine an initial temperature (T _f i _ltr (0)) from an initial intake air temperature (T _a i _r _i _nl ) in the engine (5) and an initial coolant temperature (Tn _{q jn} i), and an estimation module (20) capable of mathematically filtering the intake air temperature (T _a i _r (z)) in the motor (5) so as to impose on the filtered value (T _f ii _tr (z)) a maximum gradient taking over time at least two different positive values (a, A), one or the other of these maximum positive gradient values being selected according to the instantaneous speed (V (z)) of the vehicle (1) ·